The present invention relates to a method of making a green tire being capable of improving tire uniformity by decreasing a variation of the carcass cord lengths.
In general, in the manufacture of pneumatic tires, in order to make a green tire, an inner liner of gas-impermeable rubber, one or more strips of rubberized cords for a carcass ply, reinforcing layer, etc. are wound on a building drum. The elastomers used in such rubber material and rubberized materials are not yet vulcanized when wound around the-building drum. Therefore, their own adhesiveness is utilized to fix these materials onto the drum. As to the unvulcanized carcass ply material, it is first wound into a substantially cylindrical shape, and then the shape is gradually changed to the finished shape or a troidal shape. In this process, if disarrangement of carcass cords is caused, the carcass cord lengths between the bead cores in the finished tire are varied because the carcass cords"" paths are varied. Even if the variation is small, under high-speed running conditions in particular, deterioration in tire uniformity such as radial run-out becomes not ignorable.
It is therefore, an object of the present invention to provide a method of making a green tire, in which disarrangement of the carcass cords is prevented so that the carcass cords"" paths become constant and thereby the deterioration in the tire uniformity due to the cord path variation can be avoided.
According to the present invention, in method of making a green tire comprises
winding a carcass ply of rubberized cords around a building drum into a substantially cylindrical body,
pressing the cylindrical body against the building drum through the entire circumference not to allow the carcass cords to move axially and circumferentially of the drum,
constricting edge portions of the substantially cylindrical body so that the outer diameter thereof is decreased,
setting a bead core around each of the constricted edge portions,
folding back the edge portions around the bead cores,
swelling a main portion of the cylindrical body between the bead cores while decreasing the width between the bead cores.